Recently, there is an accelerating demand to mount touch panels as the screen on mobile phones and other displays. While the touch panel has a screen kept bare, there are many chances of the finger or cheek coming in direct contact with the screen. Undesirably the touch panel is readily fouled with stains like sebum. There is an increasing need for technology to attain fingerprint proofness or easy stain removal on a display surface for better appearance or visibility. It is thus desired to have a material capable of meeting these requirements. In particular, for touch panel displays which are readily stained with fingerprints, it is desirable to form a water/oil repellent layer on their surface. Prior art water/oil repellent layers have high water/oil repellency and easy stain wipe-off, but suffer from the problem that the antifouling performance deteriorates during service.
Generally, fluoropolyether-containing compounds exhibit, by virtue of their extremely low surface free energy, water/oil repellency, chemical resistance, lubricity, parting, antifouling and other properties. Taking advantage of these properties, they find use in a variety of industrial fields as water/oil repellent antifouling agents for paper and textiles, lubricants for magnetic recording media, oil-repellent agents for precision instruments, parting agents, cosmetic ingredients, protective films and the like. Inversely, the same properties indicate non-tackiness or non-adhesion to other substrates. Even if they can be coated to the substrate surface, it is difficult for the coating to tightly adhere thereto.
On the other hand, silane coupling agents are well known for their ability to bond surfaces of glass or fabric substrates to organic compounds. They are widely used as surface coating agents for numerous substrates. The silane coupling agent contains an organic functional group and a reactive silyl group (typically hydrolyzable silyl such as alkoxysilyl) in the molecule. In the presence of airborne moisture or the like, the hydrolyzable silyl groups undergo self-condensation reaction to form a coating. As the hydrolyzable silyl groups form chemical and physical bonds with the surface of glass or metal, the coating becomes a tough coating having durability.
Patent Documents 1 to 5 disclose a composition predominantly comprising a fluoropolyether-containing polymer-modified silane which is obtained by introducing a hydrolyzable silyl group into a fluoropolyether-containing compound, the composition being tightly adherent to the substrate surface and capable of forming a coating with water/oil repellency, chemical resistance, lubricity, parting, antifouling and other properties.
Lenses and antireflective coatings, when treated with the fluoropolyether-containing polymer-modified silane, are improved in lubricity and parting property, but lack abrasion resistance and weather resistance.